Electromagnetic oscillating pumps are well known in the art. Typically, an electromagnetic coil is utilized to move an armature carried by an impeller relative to the frame assembly of the pump. Upon energization, a bellows-shaped discharge end of the impeller, defining a discharge chamber, is compressed, thereby decreasing the volume of the discharge chamber. This decrease in volume forces the liquid inside the chamber out of the pump through a one-way discharge valve.
Upon de-energization, a spring or permanent magnet returns the impeller to its original position or beyond, thereby increasing the volume of the discharge chamber. As a result, a partial vacuum is created inside the discharge chamber, and liquid is drawn from an inlet end of the impeller, past a center valve, and into the discharge chamber. The electromagnetic coil is then re-energized and the cycle is repeated, thereby producing a stop-and-go flow in one direction. Oscillations on the order of 60 times per second, however, create a flow that is substantially continuous.
Currently, the oscillating pumps known in the art use springs or a permanent magnet as the opposing force to the electromagnetic forces. McNaull U.S. Pat. No. 5,567,131, for example, discloses an electromagnetic oscillating pump using a spring biased valve and a return spring to retract the armature. At least one disadvantage to using springs, however, is that they add unnecessary complexity to the pump, thereby increasing the costs and the possibility of a mechanical failure. In addition, springs and permanent magnets often provide an excessive return force which diminishes the efficiency or performance of the electromagnetic coil.
The present invention is advantageous in that it is simpler to use, manufacture, and maintain, and is less expensive and more reliable than those devices known in the art. Therefore, the need exists for an electromagnetic oscillating pump that does not require springs, a permanent magnet, or other mechanical devices to provide the return force for the armature.